The present invention relates to systems and methods for facilitating communications and data content transfer between a base station and a mobile platform via a satellite based transponder. More particularly, the present invention relates to such a system and method which provides routing information in a forward link signal to the mobile platform which the mobile platform returns to the base station in a return link signal, thereby informing the base station of the precise route through various components in the forward communications link path that the forward link signal took in reaching the mobile platform.
Broadband data and video surfaces, on which our society and economy have grown to depend, have heretofore generally not been readily available to users on board mobile platforms such as aircraft, ships, trains, automobiles, etc. While the technology exists to deliver such services to all forms of mobile platforms, past solutions have been generally quite expensive, low data rate and/or available to only very limited markets of government/military users and some high-end maritime markets (i.e., cruise ships).
At present, a wide variety of data services can be provided via a satellite link from a ground-based radio frequency transceiver. Such data services may include conventional Internet services such as email, web browsing, net meeting, as well as virtual private networks (VPNs) for corporate and government customers.
One particular problem with establishing communication links between numbers of mobile platforms operating within a given coverage region, and a single base station, for example a ground-based RF transceiver, is the difficulty in quickly establishing communications links with each of the mobile platforms. For example, with commercial air traffic dozens of aircraft may be moving into and out of a given coverage region throughout any given time period. In this situation, it is critical that each aircraft be able to quickly establish a communications link with the base station within the coverage region which it is traversing without interfering with communication links already established with the base station by other aircraft. It is also important that the bandwidth assigned to any given aircraft can be modified to accommodate, as best as possible, the bandwidth demands of each aircraft to handle the volume of data content being transmitted from the aircraft back to the ground station.
It is also important that any such system as described above which is intended to facilitate a return communications link for a mobile platform, such as an aircraft, needs to be able to quickly deduce that the aircraft is not responding to a polling signal and then to reallocate the specific return channel to other aircraft which may be requesting additional bandwidth to handle increased data rate transmission needs.
Another important consideration is the ability to maintain an accounting of which components a xe2x80x9cforward linkxe2x80x9d signal passes through before it is received by a mobile platform while using the least amount of bandwidth in reporting this path. By xe2x80x9cforward linkxe2x80x9d it is meant a signal that is transmitted from a base station, typically including a ground based RF transceiver, to the mobile platform. For any base station attempting to receive RF communications from a plurality of mobile platforms via a transponder, a number of independent components such as modulators and satellite based transponders may need to be employed. The system will also need to maintain an accounting of which modulators and transponders are being used by which mobile platform as the mobile platform transmits data or other information back to the base station. Normally, such information would require additional bandwidth as it would be transmitted back from the mobile platform in a separate message to the ground station. A transmission of data or other information from the mobile platform back to the base station can be termed a xe2x80x9creturn linkxe2x80x9d transmission. By knowing at all times which components in an equipment chain of the base station, as well as which satellite based transponders, are forming forward link communications paths with a mobile platform, the base station would be able to more efficiently manage forward link traffic and the use of its forward link components. If forward link path information could be combined with other information in the return link response by the aircraft, then valuable bandwidth could be conserved as well.
The present invention relates to a system and method for enabling a mobile platform communicating with a base station via a satellite based RF transponder to provide pertinent information to the base station as to a xe2x80x9cpath discoveryxe2x80x9d of a signal which it receives from the base station when a communications link is being established. By xe2x80x9cpath discoveryxe2x80x9d it is meant the specific components associated with the base station, as well as specific transponders (if more than one is available to form a communications link) which form a signal path to the mobile platform. Advantageously, this path discovery information is provided together with return channel information in a single polling signal so that an inactive mobile platform can be informed as to which one of a plurality of available return channels it should respond on, and can also provide important path discovery information back to the base station in its return link transmissions. Combining this path discovery information with the preliminary return channel information saves significant transponder bandwidth.
With the present invention, the path discovery information is provided in the body of forward link polling messages transmitted to the mobile platform via the satellite based transponder. The mobile platform, in its return link transmissions, includes this path discovery information. This informs the base station as to exactly which of its components have been used to form a communications link or links with the mobile platform. Since the base station will typically employ a plurality of components, such as RF modulators, and since it is anticipated that a plurality of satellite transponders may be employed to handle the return link traffic, it becomes important for the base station to know at all times exactly which of its components, as well as which transponders, are forming communications links with specific mobile platforms that have each established a return communication link with it. In this manner the base station is able to effectively manage its resources (i.e., components) to maintain a plurality of independent communications links with a corresponding plurality of mobile platforms. Just as importantly, combining the path discovery information with the polling signals and having the mobile platform transmit this information back to the base station with its response saves transponder bandwidth.